Unintelligibility

Overview: 

Unintelligibility refers to speech that is extremely difficult or impossible for listeners to understand. A person’s speech may be unintelligible due to numerous factors: severe articulation or phonological errors (e.g., numerous sound substitutions/omissions in children with a phonological disorder), motor speech disorders such as dysarthria (where imprecise articulation, voice, or prosody reduce clarity), or structural/anatomical issues like cleft palate. When speech is unintelligible, even familiar listeners struggle to discern words or meaning without context.

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SLPs assess intelligibility both quantitatively (percent of words understood) and qualitatively (identifying error patterns contributing to breakdown). High unintelligibility can significantly impact a person’s academic, social, and vocational participation. Clinically, improving intelligibility is often a primary goal – therapy may target correct production of sounds (articulation therapy), use augmentative communication as a supplement, or teach strategies like slowing rate or using gestures to aid listener comprehension. The ultimate aim is to make the speaker’s intended message more accessible to listeners, thereby enhancing functional communication.

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Sources:

Coplan, J., & Gleason, J. R. (1988). Unclear speech: Recognition and significance of unintelligible speech in preschool children. Pediatrics, 82(3 Pt 2), 447–452. (Provides benchmarks for intelligibility—e.g., by age 4 speech should be fully understood.) PubMed: Link

Kent, R. D., Miolo, G. M., & Bloedel, S. B. (1994). The intelligibility of children’s speech: A review of evaluation measures. American Journal of Speech‑Language Pathology, 3(3), 81–95. Link